The invention relates to a process for the continuous welding of guided and abutted strips or plates, using a laser beam to which follow-up process gas is supplied at the welding location, the weld being cooled with a sprayed-on coolant adjacent to the location of welding.
The invention also relates to an apparatus for the continuous welding of guided and abutted strips or plates, using guiding and conveying means and also a fixed laser radiator which is followed in the conveying direction of the strips or plates by a nozzle arrangement having a process gas nozzle directed at the welding point and a coolant nozzle directed at the immediate surroundings of the location of welding.
Processes for the laser beam continuous welding of guided and abutted strips or plates are known (DE 195 37 924 A1; EP 0 450 349 B1).
In one of these prior art devices (DE 195 37 294 A1) three nozzles are disposed one after the other in the conveying direction of the strips, protective gas being supplied to the welding location via a first nozzle. Inert gas is blown on to the weld via a following nozzle. The weld is acted upon by a liquid coolant via a third nozzle. The inert gas of the second nozzle and the liquid coolant are directed away from the welding location at a certain angle. In practice the inert gas of the second nozzle produces a gas curtain which screens the welding location from the coolant.
Such an apparatus is expensive, since it requires three separate supply lines for gas and coolant. Another disadvantage is that in view of the given geometrical relationships with the three nozzles, cooling cannot start very close to the welding location. Nor can the relationships be simply altered in dependence on the process. Corrosion can be prevented only if after cooling the liquid coolant is removed by suction from the strip surface. This requires an expensive suctional removal device.
In the other known apparatus (EP 0 450 349 B1) the cooling nozzle consists of a cooling plate having a plurality of nozzle openings, and a beak which also has a plurality of nozzle openings and extends as far as adjacent the welding location. In this case, air is blown on as coolant over the nozzle apertures. Quite apart from the very expensive construction of this cooling plate, experience shows that particularly intensive cooling cannot be achieved using air.
A more intensive cooling of the welding place is supposed to be obtained by means of a gas/liquid coolant mixture applied by nozzle (SU 18 24 268 A1).
It is an object of the invention to provide a process and an apparatus for the continuous welding of guided and abutted strips or plates using a laser beam, said process and apparatus enabling the weld to be intensively cooled using comparatively simple means.